1. Field of the Invention
This invention relates to the measurement of the fundamental frequency of a musical tone and in particular is concerned with a system for indicating the deviation of a musical tone from a prespecified frequency.
2. Description of the Prior Art
Musicians are almost daily faced with the task of tuning their instruments to some prespecified frequency. The usual standard frequency is A.sub.4 =440 Hz. This tuning procedure can be tedious and represents a challenge for many musicians depending upon their current maturity.
A possible approach to the tuning procedure would be to use a microphone coupled to a frequency measuring instrument. Such an approach can be somewhat slow and the equipment might be expensive. Usually the musician does not really want a true measure of a musical tone's frequency. Instead he wishes an indication of whether or not a note played on his instrument is flat or short with respect to a prespecified standard pitch, or frequency, as well as some simple measure of how much the instrument's tone differs from the standard pitch.
The musician generally knows the octave and the note within the octave for the played note. This information can be used to set controls on the tuning device. Tuning devices using preset switches have been manufactured. However it is convenient, especially when a group of musicians wish to share a common tuning indicator, to have a tuning device which does not require switches to be selected to correspond to a priori knowledge of an octave and the note within the octave.
It is an object of the present invention to provide an indication of the offset of a musical tone from a prespecified standard frequency without using a priori knowledge of the octave or musical note within the octave.
A tuning indicator is essentially a calibrated spectrum analyzer having analysis filters corresponding to the frequencies of the musical scale. It is a further object of the present invention to perform a calibrated spectral analysis of a musical tone using a system of digital logic which can be implemented using conventional state-of-the-art microelectronic devices.